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44 lines
1.6 KiB
Swift
44 lines
1.6 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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// Random access for String.UTF16View, only when Foundation is
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// imported. Making this API dependent on Foundation decouples the
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// Swift core from a UTF16 representation.
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extension String.UTF16View.Index : RandomAccessIndexType {
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/// Construct from an integer offset.
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public init(_ offset: Int) {
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_precondition(offset >= 0, "Negative UTF16 index offset not allowed")
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self.init(_offset: offset)
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// self._offset = offset
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}
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/// Return the minimum number of applications of `successor` or
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/// `predecessor` required to reach `other` from `self`.
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///
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/// - complexity: O(1).
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public func distanceTo(x: String.UTF16View.Index) -> Int {
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return x._offset - _offset
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}
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/// Return `self` offset by `n` steps.
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///
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/// - returns: If `n > 0`, the result of applying `successor` to
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/// `self` `n` times. If `n < 0`, the result of applying
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/// `predecessor` to `self` `-n` times. Otherwise, `self`.
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///
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/// - complexity: O(1)
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public func advancedBy(x: Int) -> String.UTF16View.Index {
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return String.UTF16View.Index(_offset: _offset + x)
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}
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}
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